Preparation of nanostructured mixed lithium-zirconium oxides by spray pyrolysis

Abstract

This invention relates to a method for producing lithium zirconium mixed oxide by flame spray pyrolysis, the mixed oxide obtained by the method, and its use in lithium-ion batteries.

Description

Field of the invention

[0001] The present invention relates to a process for the production of lithium zirconium mixed oxides by flame spray pyrolysis, the mixed oxides obtainable from the process and the use thereof in lithium ion batteries. State of the art

[0002] Secondary lithium ion batteries are one of the most important battery types in use today. Secondary lithium ion batteries are typically composed of an anode made of carbon material or lithium metal alloy, a cathode made of lithium-metal oxides, a liquid electrolyte in which a lithium salt is dissolved in an organic solvent and a separator which provides a passage for lithium ions between the positive and negative electrode during the charging and discharging process.

[0003] In an effort to develop secondary batteries with improved intrinsic safety and energy density, recent advances have been made using solid electrolytes instead of liquid electrolytes. Such all-solid-state secondary lithium ion batteries should have good ionic conductivity at the interface between the electrode active material and the electrolyte to have the required load characteristics. This high ionic conductivity can be achieved by coating the surface of the active electrode material with some lithium-containing compound such as LiTi2(P04)3 as described in JP 4982866 B2.

[0004] Lithium-containing mixed oxides have various applications in both solid state and liquid state lithium ion batteries.

[0005] One of the general problems of cathode materials for lithium ion batteries is their fast aging, so that the performance is lost during cycling. It is well known that coating or doping mixed lithium transition metal oxide particles with some metal oxides can suppress the undesired reaction of the electrolyte with the electrode material and thus improve the long-term stability of lithium ion batteries.

[0006] Among other metal oxides, lithium-containing mixed oxides with zirconium have been reported for this purpose.

[0007] US2017179544A discloses the preparation of lithium cathode materials doped with zirconium-based mixed metal oxides. Thus, in Example 1, Li7La3Zr2Al 0.07 O 12.0105 is prepared by mixing the metal salts and sintering the mixture at 1200 °C for 10 hours, followed by dry mixing with the mixed lithium transition metal oxide Li(Li 10 / 75 Ni 18 / 75 Co 9 / 75 Mn 38 / 75 )02and subsequent heating at 900 °C for 20 hours to form the lithium cathode material. It is evident from this preparation process that only large-sized sintered particles of Li7La3Zr2Al 0.07 O 12.0105 can be used in this example.

[0008] The use of such relatively large zirconium-containing metal oxide particles typically results in a non-uniform distribution of large agglomerated metal oxide particles on the surface of the core cathode material, thus, little or no improvement in the cycling performance is observed when compared to the undoped or uncoated cathode material.

[0009] Ceramic transactions (1997), 85, pages 55-66 describes the preparation of Li2Zr03powder with primary particles of less than 20 nm and a BET surface area of 10-14 m 2 / g by a combustion process starting from an aqueous solution of zirconium nitrate and lithium nitrate precursors. Urea and citric acid are added as fuels to the aqueous solution of the metal precursors. Heating of the resulting mixture leads to complete evaporation of water followed by combustion of the metal precursors and the fuels. Although relatively small sized metal oxide particles are provided, this process is difficult to apply industrially, in particular for the continuous production of large amounts of the corresponding lithium-zirconium mixed oxides.

[0010] Spray pyrolysis is a known method for the production of relatively small metal oxide particles.

[0011] Spray pyrolysis and flame spray pyrolysis are established methods for the production of simple metal oxides as well as complex mixed metal oxides. In spray pyrolysis, metal compounds in the form of fine droplets are introduced into a high-temperature zone, where they are oxidized and / or hydrolyzed to give metal oxides. A special form of this process is flame spray pyrolysis, in which the droplets are supplied to a flame formed by igniting a fuel gas and an oxygen-containing gas.

[0012] IN2010K000216 describes a spray pyrolysis method for the synthesis of nanostructured lithium zirconate powder using water-based precursor solutions. Thus, the examples of this patent application show the preparation of lithium zirconate with a BET surface area of 6-10 m 2 / g and a compaction density of up to 1020 g / L using aqueous solutions of zirconium nitrate or zirconyl nitrate, lithium nitrate and urea or glycine.

[0013] Problem and solution

[0014] The cited prior art documents teach the manufacture of mixed lithium zirconium oxides by spray pyrolysis. However, the resulting products are reported to have a relatively large compaction density and a relatively low BET surface area, indicating a relatively large aggregate particle size of such particles.

[0015] The problem addressed by the present invention is to provide an improved method for the industrial manufacture of mixed lithium zirconium oxides useful in lithium ion batteries, in particular as coating or doping material for electrodes, in particular cathodes, of lithium ion batteries and as additive for electrolytes of lithium ion batteries.

[0016] In particular, the method shall provide metal oxide particles having a small particle size, a high BET surface area and a low tap density.

[0017] During intensive experiments it was surprisingly found that lithium zirconium mixed oxides having the desired particle properties can be prepared by flame spray pyrolysis when using a specific combination of metal precursors and solvents.

[0018] Process for producing mixed oxides

[0019] The present invention provides a process for producing lithium zirconium mixed oxides by flame spray pyrolysis and optional further heat treatment, characterized in that

[0020] In the process a solution of at least one metal precursor is used, which comprises

[0021] - lithium and / or zirconium carboxylates, wherein each of these metal carboxylates comprises 5 to 20 carbon atoms, and

[0022] - a solvent, which comprises less than 5 wt.-% of water.

[0023] The term "lithium zirconium mixed oxide" in the context of the present invention refers to a compound or mixture of compounds comprising lithium (Li), zirconium (Zr) and oxygen (O) atoms.

[0024] During the flame spray pyrolysis process a solution of metal compounds (metal precursors) is introduced into a flame in the form of fine droplets, which is formed by igniting a fuel gas and an oxygen containing gas, wherein the used metal precursors are oxidized and / or hydrolyzed to obtain the corresponding metal oxides.

[0025] The reaction initially forms highly dispersed primary metal oxide particles of approximately spherical shape, which agglomerate during further reaction to form aggregates. The aggregates can then accumulate to agglomerates. In contrast to agglomerates, which can usually be easily separated by introducing energy, only by strongly introducing energy aggregates can be further decomposed, if at all.

[0026] The produced metal oxides are referred to as "gas phase method" or "pyrogenically produced" metal oxides.

[0027] The flame spray pyrolysis process is generally described in WO 2015173114 A1 and elsewhere.

[0028] The flame spray pyrolysis preferably comprises the following steps:

[0029] a) atomizing a solution of at least one metal precursor by an atomizer gas to provide an aerosol,

[0030] b) reacting the aerosol in the reaction space of the reactor with a flame obtained by igniting a mixture of a fuel gas and an oxygen-containing gas to obtain a reaction stream,

[0031] c) cooling the reaction stream and

[0032] d) subsequently removing the solid metal oxide from the reaction stream.

[0033] Examples of suitable fuel gases are hydrogen, methane, ethane, natural gas and / or carbon monoxide. The use of hydrogen is particularly preferred. The fuel gas is used in particular in embodiments in which it is desired that the metal oxide produced has a high crystallinity.

[0034] The oxygen-containing gas is generally air or oxygen-enriched air. The oxygen-containing gas is used in particular in embodiments in which it is desired, for example, that the metal oxide produced has a high BET surface area. The total amount of oxygen is generally chosen such that it is at least sufficient for the complete conversion of the fuel gas and the metal precursor.

[0035] To obtain the aerosol, the gasified solution comprising the metal precursor can be mixed with an atomizer gas such as nitrogen, air and / or other gases. The fine droplets of the resulting aerosol preferably have an average droplet size of 1 to 120 μηη, particularly preferably 30 to 100 μηη. The droplets are generally produced using a single- or multi- material nozzle. To increase the solubility of the metal precursor and to obtain a suitable viscosity which facilitates the atomization of the solution, the solution can be heated.

[0036] The metal precursors used in the process according to the application comprise at least one lithium carboxylate and at least one zirconium carboxylate, each comprising 5 to 20 carbon atoms.

[0037] The carboxylate salts of lithium and zirconium used in the process according to the application can be, independently of one another, lithium and / or zirconium straight-chain, branched or cyclic pentanoates (C5), hexanoates (C6), heptanoates (C7), octanoates (C8), nonanoates (C9), decanoates (C10), undecanoates (Cn), dodecanoates (C12), tridecanoates (C13), tetradecanoates (C14), pentadecanoates (C15), hexadecanoates (C16), heptadecanoates (C17), octadecanoates (C18), nonadecanoates (C19), icosanoates (C20) and mixtures thereof.

[0038] Most preferably, zirconium 2-ethylhexanoate (C8) and lithium neodecanoate (C10) are used.

[0039] The solvents used in the process according to the application are preferably selected from the group consisting of alcohols, ethers, esters, carboxylic acids, optionally halogenated hydrocarbons and mixtures thereof.

[0040] The alcohol can be selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, n-hexanol, cyclohexanol, n-octanol, 2-ethylhexanol, n-decanol, neodecanol and mixtures thereof.

[0041] The ester can be an alkyl ester of a carboxylic acid, such as ethyl acetate.

[0042] The carboxylic acid preferably comprises 1 to 20 carbon atoms and is preferably selected from the group consisting of acetic acid; straight-chain, branched or cyclic propionic acid (C3), butyric acid (C4), valeric acid (C5), caproic acid (C6), heptanoic acid (C7), caprylic acid (C8), pelargonic acid (C9), capric acid (D10), undecanoic acid (C11), lauric acid (C12), tridecanoic acid (C13), myristic acid (C14), pentadecanoic acid (C15), palmitic acid (C16), margaric acid (C17), stearic acid (C18), nonadecanoic acid (C19), arachidic acid (C20) and mixtures thereof.

[0043] The hydrocarbon can be straight-chain, branched, cyclic aliphatic, aromatic or mixed aliphatic / aromatic. Suitable examples thereof include benzene, toluene, naphtha and petroleum solvent oil.

[0044] Examples of halogenated hydrocarbons include chloroform (CHCI3), dichloromethane (CH2CI2), carbon tetrachloride (CCI4).

[0045] Most preferably, a mixture of a hydrocarbon and a carboxylic acid, for example a mixture of naphtha and 2-ethylhexanoic acid, is used as solvent.

[0046] The solvent used in the present application comprises less than 5 wt.-% of water, preferably less than 3 wt.-% of water, more preferably less than 2 wt.-% of water, even more preferably less than 1 wt.-% of water, still more preferably less than 0.5 wt.-% of water.

[0047] Most preferably, the solvent is essentially free of water, i.e. the water content in the solvent is less than 0.1 wt.-%, more preferably less than 500 ppm, even more preferably less than 200 ppm.

[0048] The total metal content in the solution of metal precursors is preferably 1 to 30 wt.-%, more preferably 2 to 20 wt.-%, even more preferably 3 to 15 wt.-%. The "total metal content" is to be understood as the total weight proportion of all metals contained in the metal precursors in the solution of metal precursors used.

[0049] The solvent mixture used in the process of the present application can additionally comprise a chelating agent, i.e. a compound capable of forming two or more coordination bonds with metal ions. Examples of such chelating agents are, for example, diamines such as ethylenediamine, ethylenediaminetetraacetic acid (EDTA), 1,3-dicarbonyl compounds such as acetylacetone and alkyl acetoacetates. Most preferably, acetylacetone is used as such chelating agent.

[0050] It was observed that zirconium precursors exhibited better solubility in the presence of such chelating agents and did not precipitate after relatively long storage periods.

[0051] Using a specific combination of the metal carboxylates according to the invention and solvents with reduced water content allows for ensuring good solubility of the metal precursors and achieving desired metal oxide particle properties, such as small particle size, high BET surface area, and low compaction density.

[0052] The method of the present invention includes optionally further heat treatment of the mixed oxide prepared by flame spray pyrolysis.

[0053] The further heat treatment is preferably carried out at a temperature of 500°C-1200°C, more preferably at 550°C-1150°C, even more preferably at 600°C-1100°C, and even more preferably at 650°C-1050°C.

[0054] The heat treatment according to the method of the present invention allows for the acquisition of heat-treated mixed oxides with desired properties, particularly desired chemical phases, crystal structures, etc. Therefore, untreated lithium-zirconium mixed oxides prepared directly by flame spray pyrolysis can comprise a mixture of ZrO2, Li2O, Li2ZrO3, and other compounds. Heat treatment of this mixture at a temperature of approximately 600°C–800°C allows for the additional formation of Li2ZrO3 and Li4Zr3O8 phases, making the latter the dominant chemical phase present in the heat-treated mixed oxide.

[0055] Mixed oxides

[0056] The mixed oxide prepared by the method according to the present invention preferably has a content of 0.1 m. 2 / g-100m 2 / g of BET surface area.

[0057] Untreated mixed oxides, i.e., products of the method of the present invention that have not undergone further heat treatment, preferably have a 5m content. 2 / g-100m 2 / g, more preferably 7m 2 / g-70m 2 / g, optimal value 15-50m 2 / g of BET surface area.

[0058] The heat-treated mixed oxide, i.e., the product of the method of the present invention subjected to further heat treatment, preferably has a content of less than 20 μm. 2 / g, more preferably 0.1m 2 / g-10m 2 / g, more preferably 0.2m 2 / g-5m 2 / g, optimal value 0.3-3m 2 / g of BET surface area.

[0059] The surface area of ​​BET can be determined according to DIN 9277:2014 by nitrogen adsorption according to the Brunauer-Emmett-Teller procedure.

[0060] As determined by transmission electron microscopy (TEM), the mixed oxide prepared by the method according to the invention is typically in the form of aggregated primary particles with a number-average diameter of 5-100 nm, preferably 7-70 nm, and more preferably 10-50 nm. This number-average diameter can be determined by calculating the average size of at least 500 particles analyzed by TEM.

[0061] Number-average particle size d of (aggregated and agglomerated) mixed oxides 50 The number-average diameter is typically about 0.05 μm to 2 μm, more preferably 0.05 μm to 1 μm, and even more preferably 0.05 μm to 0.5 μm. This number-average diameter can be determined by static light scattering (SLS) in a suitable dispersion, for example, in an aqueous dispersion.

[0062] Agglomerates and a subset of aggregates can be broken down, for example by grinding or sonicating the particles to produce particles with smaller particle size and a narrower particle size distribution.

[0063] Preferably, the average particle size d of the mixed oxides 50 The wavelength is 10-150 nm, more preferably 20-130 nm, and even more preferably 30-120 nm, as determined by static light scattering (SLS) after ultrasonic treatment of a mixture consisting of 5% by weight particles and 95% by weight of a 0.5 g / L sodium pyrophosphate aqueous solution at 25 °C for 300 seconds.

[0064] (d) particles of zirconium dioxide and / or zirconium-containing mixed oxides 90 -d 10 ) / d 50 The range is preferably 0.4-1.2, more preferably 0.5-1.1, and even more preferably 0.6-1.0, as determined by static light scattering (SLS) after ultrasonic treatment of a mixture consisting of 5% by weight particles and 95% by weight of a 0.5 g / L sodium pyrophosphate aqueous solution at 25 °C for 300 seconds.

[0065] Therefore, the mixed oxides prepared by the method of the present invention preferably have the characteristics of small particle size and narrow particle size distribution. This facilitates the achievement of high-quality metal oxide doping and / or coating of active electrode materials for lithium-ion batteries.

[0066] d value d 10 d 50and d 90 It is typically used to characterize the cumulative particle size distribution of a given sample. For example, d 10 The diameter is less than d 10 The diameter d when the particles occupy 10% of the sample volume. 50 It is less than d 50 The diameter when the particles occupy 50% of the sample volume. d 50 Also known as the "median diameter of volume" because it divides the sample into equal volumes; d 90 It is less than d 90 The diameter when the particles occupy 90% of the sample volume.

[0067] The mixed oxides prepared by the method according to the present invention preferably have a tamped density of 20 g / L to 1000 g / L.

[0068] The untreated mixed oxide prepared by the method according to the present invention preferably has a compaction density of 20 g / L-300 g / L, more preferably 30 g / L-270 g / L, even more preferably 40 g / L-250 g / L, and still more preferably 50 g / L-200 g / L.

[0069] The heat-treated mixed oxide prepared by the method according to the present invention preferably has a compaction density of 200 g / L-800 g / L, more preferably 250 g / L-750 g / L, and even more preferably 300 g / L-700 g / L.

[0070] The compacted density of powdery or coarse-grained granular materials can be determined according to DIN ISO 787-11:1995 “General methods of test for pigments and extenders—Part 11: Determination of tamped volume and apparent density after tamping”. This involves measuring the apparent density of the bed after mixing and compaction.

[0071] The mixed oxide prepared by the method of the present invention is preferably inherently hydrophilic, meaning that it is not further treated with any hydrophobic reagents such as silanes after synthesis by flame spray pyrolysis. The particles thus produced typically have a purity of at least 96% by weight, preferably at least 98% by weight, more preferably at least 99% by weight, where 100% purity means that the mixed oxide contains only specific metals and oxygen. The mixed oxide may contain hafnium compounds in the form of hafnium dioxide. Based on ZrO2, the proportion of hafnium dioxide can be 1-4% by weight. Based on the mass of the mixed oxide powder, the chloride content is preferably less than 0.5% by weight, more preferably less than 0.1% by weight. Based on the mass of the mixed oxide powder, the carbon proportion is preferably less than 2% by weight, more preferably 0.005-1% by weight, and even more preferably 0.01-0.5% by weight.

[0072] Mixed oxides are preferably compounds having the following general formula.

[0073] Li a Zr b O 0.5a+2b ,

[0074] in

[0075] 0.5≤a≤12, preferably 2.0≤a≤8;

[0076] 1.0≤b≤4.0, preferably 1.0≤b≤2.0;

[0077] Preferably, the composition of the mixed oxide of the present invention corresponds to one of the following formulas: Li2ZrO3, Li4Zr2O6, Li4ZrO4, Li4Zr3O8, Li6Zr3O9, Li8ZrO6, with Li2ZrO3 being the most preferred.

[0078] This invention also provides a lithium-zirconium mixed oxide.

[0079] in

[0080] -The mixed oxides are in the form of aggregated primary particles,

[0081] -with 15-50m 2 / g BET surface area.

[0082] Number-average particle size d = -0.05-1 μm 50 For example, determined by static light scattering (SLS), and

[0083] Compacted density of -50 to 200 g / L.

[0084] Such mixed oxides can be prepared by the method of the present invention without further heat treatment.

[0085] This invention also provides a lithium-zirconium mixed oxide.

[0086] in

[0087] -The mixed oxides are in the form of aggregated primary particles,

[0088] -with less than 20m 2 / g, preferably 0.1-20m 2 / g BET surface area.

[0089] Number-average particle size d = 1-50 μm 50 For example, determined by static light scattering (SLS), and

[0090] Compacted density of -200-800 g / L.

[0091] Such mixed oxides can be prepared by the method of the present invention, wherein further heat treatment is performed.

[0092] The present invention also provides a mixed oxide that can be obtained by the method of the present invention.

[0093] Applications of mixed oxides in lithium-ion batteries

[0094] The present invention also provides the use of the mixed oxide according to the invention or the mixed oxide that can be obtained by the method of the present invention in lithium-ion batteries, particularly as a coating or doping material for the electrodes, especially the cathodes, of lithium-ion batteries, or as an additive for liquid electrolytes, gel electrolytes, or solid electrolytes of lithium-ion batteries.

[0095] The present invention also provides a lithium-ion battery comprising a mixed oxide according to the present invention or a mixed oxide obtainable by the method of the present invention.

[0096] In addition to the active positive electrode (cathode), the lithium-ion battery of the present invention may also include an anode, a separator, and an electrolyte containing a lithium compound.

[0097] The positive electrode (cathode) of a lithium-ion battery typically includes a current collector and an active cathode material layer formed on the current collector.

[0098] The current collector can be aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, polymer substrate coated with conductive metal, or a combination thereof.

[0099] The active cathode material may include materials capable of reversibly inserting / deintercalating lithium ions and is well known in the art. Such active cathode materials may include transition metal oxides, such as mixed oxides comprising Ni, Co, Mn, V or other transition metals and optionally lithium. Preferred mixed lithium transition metal oxides used as active cathode materials are selected from lithium-cobalt oxides, lithium-manganese oxides, lithium-nickel-cobalt oxides, lithium-nickel-manganese-cobalt oxides, lithium-nickel-cobalt-aluminum oxides, lithium-nickel-manganese oxides, or mixtures thereof. The mixed lithium transition metal oxide preferably has the general formula LiMO2, wherein M is at least one transition metal selected from nickel, cobalt, and manganese; more preferably, M = Co or Ni. x Mn y Co z , where 0.3≤x≤0.9, 0≤y≤0.45, 0≤z≤0.4.

[0100] The anode of a lithium-ion battery can comprise any suitable material capable of reversibly inserting / deintercalating lithium ions, typically used in secondary lithium-ion batteries. Typical examples are carbonaceous materials, including crystalline carbon such as natural or artificial graphite in the form of plate-like, flake-like, spherical, or fibrous graphite; and amorphous carbon such as soft carbon, hard carbon, mesophase pitch carbides, coke, or mixtures thereof. Additionally, lithium metal or conversion materials (e.g., Si or Sn) can be used as the anode active material.

[0101] The electrolyte in a lithium-ion battery can be in liquid, gel, or solid form.

[0102] The liquid electrolyte of a lithium-ion battery may include any suitable organic solvent commonly used in lithium-ion batteries, such as anhydrous ethylene carbonate (EC), dimethyl carbonate (DMC), isopropylene carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxyethane, fluoroethylene carbonate, vinyl ethylene carbonate, or mixtures thereof.

[0103] Gel electrolytes include gel polymers.

[0104] The solid electrolyte of a lithium-ion battery may contain oxides, such as lithium metal oxides, sulfides, phosphates, or solid polymers.

[0105] The liquid or gel electrolyte of lithium-ion batteries typically contains lithium salts. Examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis-2-(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), Li2SiF6, lithium trifluoromethanesulfonate, LiN(SO2CF2CF3)2, lithium nitrate, lithium bis(oxalate)borate, lithium cyclo-difluoromethane-1,1-bis(sulfonyl)imide, lithium cyclo-hexafluoropropane-1,1-bis(sulfonyl)imide, and mixtures thereof.

[0106] Lithium-ion batteries, especially those with liquid or gel electrolytes, may also include a separator to prevent direct contact between the two electrodes that could lead to an internal short circuit.

[0107] The diaphragm material may include polyolefin resins, fluorinated polyolefin resins, polyester resins, polyacrylonitrile resins, cellulose resins, nonwoven fabrics, or mixtures thereof. Preferably, the material includes polyolefin resins such as polyethylene or polypropylene-based polymers, fluorinated resins such as polyvinylidene fluoride polymers or polytetrafluoroethylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyacrylonitrile resins, cellulose resins, nonwoven fabrics, or mixtures thereof.

[0108] Brief description of the attached figures

[0109] Figure 1A and 1B This is a TEM image of the Li-Zr mixed oxide particles prepared as described in Example 1.

[0110] Figure 2 The SEM-EDX mapping image of Zr (white) on an LZO-coated NMC is shown. This image was prepared using LZO prepared as described in Example 1.

[0111] Figure 3 SEM-EDX images of Zr (white) on an NMC coated with LZO prepared using LZO as described in Comparative Example 1 are shown.

[0112] Figure 4 Statistical analysis of the area distribution of Zr in SEM-EDX images of LZO-coated NMC prepared using LZO as described in Comparative Example 1 and Example 2 is presented.

[0113] Figure 5 The XRD patterns of the Li-Zr mixed oxide (LZO) of the present invention prepared as described in Examples 1-3 are shown. Detailed Implementation

[0114] Example

[0115] The surface area of ​​BET is 0.30-0.60 m². 2 / g, median particle size d 50 A commercially available mixed lithium nickel manganese cobalt oxide powder NMC (7-1.5-1.5) (PLB-H7 type) with a diameter of 10.6 ± 2 μm (determined by static laser scattering) was provided by Linyi Gelon LIB Co.

[0116] BET surface area is less than 1m 2 / g, median particle size d 50 Commercially available lithium zirconium oxide powder (LZO, type 2004PR) with a thickness of 19.3 ± 2 μm (determined by static laser scattering) was supplied by Sigma Aldrich.

[0117] Comparative Example 1

[0118] (Li-Zr mixed oxides from nitrate precursor aqueous solution)

[0119] An aqueous solution containing 630 g LiNO3 and 1733 g Zr(NO3)4 (metal content 24 wt%) was prepared under vigorous stirring until all solid contents dissolved. This solution represents the theoretical composition of Li2ZrO3.

[0120] The aerosol consists of a solution flow of 2.5 kg / h and 15 Nm. 3 An airflow of / h is formed via a two-component nozzle and sprayed into the tubular reactor under combustion flame conditions. The combustion gases of the flame are 13Nm³. 3 / h of hydrogen and 75Nm 3 The air composition is / h. In addition, 25Nm was used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0121] The particle properties are shown in Table 1.

[0122] Preparation of NMC powder coated with the Li-Zr mixed oxide of Comparative Example 1:

[0123] First, NMC powder (99 g) was mixed with 1.0 g (1 wt%) of the vapor-phase powder of Comparative Example 1 for 1 minute at 500 rpm (specific power: 350 W / kg NMC) in a high-intensity laboratory mixer (Somakon mixer MP-GL with a 0.5 L mixing unit) to homogenize the two powders. Then, the mixing intensity was increased to 2000 rpm (specific power: 800 W / kg NMC, tip speed of the mixing tool in the mixing unit: 10 m / s) and mixing continued for 5 minutes to achieve dry coating of NMC particles with the vapor-phase powder of Comparative Example 1.

[0124] Comparative Example 2

[0125] (Li-Zr mixed oxides from nitrate precursor ethanol solution)

[0126] An 8.32 kg ethanol solution containing 450 g LiNO3 and 1238 g Zr(NO3)4 (metal content 24 wt%) was prepared under vigorous stirring until all solid contents were dissolved. This solution represents the theoretical composition of Li2ZrO3.

[0127] The aerosol consists of a solution flow of 2.5 kg / h and 15 Nm. 3 An airflow of / h is formed via a two-component nozzle and sprayed into the tubular reactor under combustion flame conditions. The combustion gases of the flame are 6.8 Nm³. 3 / h of hydrogen and 75Nm 3 The air composition is / h. In addition, 25Nm was used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0128] The particle properties are shown in Table 1.

[0129] Example 1

[0130] 7.94 kg contains 2725 g of commercially available solution ( Deca Lithium 2, containing 2 wt% lithium in the form of lithium neodecanoate) and 2984 g of commercially available solution (Octa) A solution of Zirconium 12, containing 12 wt% zirconium ethylhexanoate (Zr) and 2231 g of 2-ethylhexanoic acid, was mixed to obtain a clear solution. This solution represents the theoretical composition of Li₂ZrO₃.

[0131] The aerosol consists of a solution flow of 2.5 kg / h and 15 Nm. 3 An airflow of / h is formed via a two-component nozzle and sprayed into the tubular reactor under combustion flame conditions. The combustion gases of the flame consist of 4Nm³. 3 / h of hydrogen and 75Nm 3 The air composition is / h. In addition, 25Nm was used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0132] The particle properties are shown in Table 1. TEM images of the particles are shown below. Figure 1A and 1B As shown in the image.

[0133] XRD analysis ( Figure 5 This indicates that the main phase of the product is still ZrO2.

[0134] Example 2

[0135] (Calcinated Li-Zr mixed oxide)

[0136] The mixed oxide obtained in Example 1 was calcined at 700°C in a rotary kiln for 6 hours. XRD analysis ( Figure 5 This indicates that the main phase of the product is a tetragonal lithium zirconium oxide (Li4Zr3O8) structure.

[0137] Example 3

[0138] (Calcinated Li-Zr mixed oxide)

[0139] The mixed oxide obtained in Example 1 was calcined at 750°C in a rotary kiln for 6 hours. XRD analysis ( Figure 5 The results indicate that the main phases of the product are monoclinic lithium zirconium oxide (Li2ZrO3) and tetragonal lithium zirconium oxide (Li4Zr3O8) structures.

[0140] Preparation of NMC powder coated with the Li-Zr mixed oxide of Example 1:

[0141] First, NMC powder (99 g) was mixed with 1.0 g (1 wt%) of the vapor-phase powder of Example 1 for 1 minute at 500 rpm (specific power: 350 W / kg NMC) in a high-intensity laboratory mixer (Somakon mixer MP-GL with a 0.5 L mixing unit) to homogenize the two powders. Then, the mixing intensity was increased to 2000 rpm (specific power: 800 W / kg NMC, tip speed of the mixing tool in the mixing unit: 10 m / s) and mixing continued for 5 minutes to achieve dry coating of NMC particles with the vapor-phase powder of Example 1.

[0142] SEM-EDX analysis was performed on a mixed lithium transition metal oxide dry-coated with Li₂ZrO₃.

[0143] Figure 2 The SEM-EDX image of Zr (white) on NMC coated with Li₂ZrO₃ (LZO) prepared using the vapor-phase method (Example 1) is shown. Figure 3 The analytical results of NMC coated with crude LZO produced by vapor phase method (Comparative Example 1) are shown. Figure 2 and Figure 3 The axes are shown as follows: x-axis = particle diameter; left y-axis = volume percentage, right y-axis = cumulative volume percentage. The NMC mixed oxide coated with vapor-phase nano-LZO (Example 1) exhibits complete and uniform coverage of all NMC particles by LZO. Figure 2 No large LZO agglomerates were detected, indicating that the nanostructured vapor-phase LZO exhibits good dispersibility. Furthermore, no free, unattached LZO particles were found near the NMC particles, indicating strong adhesion between the coating and the substrate (NMC). In contrast, Figure 3 This indicates that only the fine LZO particles from the gas-phase coarse LZO are attached to the surface of the NMC particles. Larger LZO particles are non-dispersed and therefore unattached, located near the NMC particles. As a result, the NMC particles are not completely covered by zirconium oxide.

[0144] Figure 4 It shows Figure 2 and Figure 3 Statistical analysis was performed. The area distribution of Zr (white) in the SEM-EDX image was further analyzed using box-normal plots, with units in μm. 2 and showed Figure 2 Example 1 and Figure 3 The obvious difference in the dispersibility of Zr (white) between the comparative examples 1.

[0145] Assembly and characterization of all-solid-state lithium metal batteries

[0146] Three all-solid-state NMC_Li6SP5Cl_Li metal batteries were assembled using vapor-phase nano-LZO (Example 1) and commercially available LZO from Sigma Aldrich. A composite cathode using LZO-coated NMC was prepared at a weight ratio of NMC:Li6SP5Cl:carbon = 60:35:5. A Li-In alloy was used as the anode.

[0147] The initial impedance was analyzed by electrochemical impedance spectroscopy (EIS), and the results are shown in Table 2. Table 2 also shows the initial coulombic efficiency of the all-solid-state battery.

[0148] Table 1: Properties of Lithium-Zirconium Mixed Oxides

[0149] Example BET[m 2 / g]]]> D 10 [μm]]]> D 50 [μm]]]> D 90 [μm]]]> Compacted density [g / L] Comparative Example 1 28 0.61 2.54 5.18 301 Comparative Example 2 17 0.14 1.05 3.24 333 Example 1 25 0.06 0.13 2.65 104 Example 2 13 0.06 0.086 2.60 350 Example 3 4.6 0.106 5.12 104 739

[0150] Table 2: Electrochemical Analysis of All-Solid-State Batteries

[0151] Example Impedance [Ω] Initial coulombic efficiency [%] No coating 1237 62.55 Coated with Example 1 139 64.46 Coated with commercial LZO 164 63.46

Claims

1. Use of lithium zirconium mixed oxides as coating material for lithium battery electrodes, characterized in that, The lithium zirconium mixed oxide is produced by flame spray pyrolysis using at least one metal precursor solution, which comprises - lithium and zirconium carboxylates, wherein each of these metal carboxylates comprises 5 to 20 carbon atoms, and - a solvent, which comprises less than 5 wt.-% of water; wherein the lithium zirconium mixed oxide is in the form of agglomerated primary particles; and The number average particle size d 50 is 0.05 - 1 μm; and the primary particles of the lithium zirconium mixed oxide have a number average diameter of 5 to 70 nm.

2. Use according to claim 1, characterized in that the flame spray pyrolysis comprises the following steps: a) atomizing the at least one metal precursor solution by an atomizer gas to provide an aerosol, b) reacting the aerosol in a reaction space of a reactor with a flame obtained by igniting a mixture of a fuel gas and an oxygen-containing gas to obtain a reaction stream, c) cooling the reaction stream and d) subsequently removing the solid metal oxide from the reaction stream.

3. Use according to claim 1 or 2, characterized in that The mixed oxide is a compound having the general formula Li a ZrbO 0.5a+2b , wherein 0.5≤a≤12， 1.0≤b≤4.0。 4. Use according to claim 1 or 2, characterized in that The mixed oxides have a BET surface area of 0.1-100 m 2 / g.

5. Use according to claim 1 or 2, characterized in that the lithium and zirconium carboxylates are independently from each other carboxylates selected from the group consisting of linear, branched or cyclic pentanoates, hexanoates, heptanoates, octanoates, nonanoates, decanoates, undecanoates, dodecanoates, tridecanoates, tetradecanoates, pentadecanoates, hexadecanoates, heptadecanoates, octadecanoates, nonadecanoates, icosanoates and mixtures thereof of lithium and / or zirconium.

6. Use according to claim 1 or 2, characterized in that the solvent is selected from the group consisting of alcohols, ethers, esters, carboxylic acids, optionally halogenated hydrocarbons and mixtures thereof.

7. Use according to claim 1 or 2, characterized in that the metal precursor solution comprises a chelating agent selected from the group consisting of diamines and 1,3-dicarbonyl compounds.

8. Use according to claim 1 or 2, characterized in that the mixed oxide has a tap density of 20 to 1000 g / L.

9. Use according to claim 1 or 2, characterized in that the lithium zirconium mixed oxide is in the form of agglomerated primary particles, having a BET surface area of 15-50 m 2 / g, Number average particle diameter d of 0.05 - 1 μm determined by static light scattering SLS 50 , and 50 to 200 g / L tap density.

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